Chitinases are widely distributed enzymes that can be classified into family 18 or family 19 glycosyl hydrolases. Family 18 chitinases are found in bacteria, fungi, viruses, vertebrates and plants while family 19 chitinases are far less abundant and were thought to occur only in higher plants and a small number of bacteria where they are involved in pathogen resistance. However, recently we have reported a novel, developmentally regulated, family 19 glycosyl hydrolase (As-p50) from the parasitic nematode, Ascaris suum-the first documented occurrence of such an enzyme in an animal species. The proposed studies are designed to further investigate the biological functions of family 19 glycosyl hydrolases in nematodes and to evaluate their importance for survival and defense by exploiting molecular and reverse genetic protocols well established in Caenorhabditis elegans, but not yet applicable to A. suum. Three putative As-p50 orthologues that display 55-63% sequence identity with As-p50 have been identified in the C. elegans genome. C08B6.4 appears to be a highly suitable surrogate to investigate the biological function(s) of As-p50 since it is expressed by hypodermal cells of C. elegans embryos and larvae with timing nearly identical to that of Asp50. Moreover, C08B6.46 also may play a role in pathogen defense since its expression appears to increase in response to infection with Drechmeria coniospora, a nematophageous fungus, that extends hyphae down the amphidial neurons in which C08B6.4 is expressed. The proposed studies will 1) clone and functionally express recombinant As-p50 and C08B6.4 to determine their catalytic and potential anti-fungal properties in vitro; 2) infect C. elegans with D. coniospora to monitor the expression of As-p50 orthologues with sqRTPCR; and 3) determine the spatial and temporal expression of the C. elegans orthologues using GFP reporter gene constructs. Since nematode family 19 glycosyl hydrolases appear to contribute to the innate immune response, they may represent potential targets for development of novel nematode control strategies. [unreadable] [unreadable]